Drum series printer with type wheels driven by individually removeable motors

ABSTRACT

The printing machine of this invention comprises a plurality of motor driven printing wheels which are selectively positioned to print out a desired line of information on a record medium. Each printing wheel is of multi-part construction having a shaft receiving hub, a rim plate fixed on the hub, and a plurality of type sectors removably, pivotally mounted on the rim plate. A platen disposed horizontally below the printing wheels is vertically displaced to print the characters on those sectors that are facing vertically downwardly at the platen printing position. Each of the sectors is free to swing under the influence of its own weight about a pivot axis extending parallel to the print wheel rotational axis as the print wheel is rotated so that when the sector is moved to its downwardly facing printing position, the weight of the sector, under the influence of gravity, will swing the sector to a position where the type on the sector is parallel to the printing surface of the platen. The sectors on each printing wheel are readily removable so that they may be replaced or arranged in a different order on the printing wheel. The print wheel hub is formed separately of the print wheel rim plate and is preferably fabricated from a relatively hard metal to minimize wear due to print wheel rotation. The hub is formed on its outer periphery with an annular, radially extending land which serves as a spacer for axially spacing the rim plate from a sprocket wheel which is drive connected by a chain to the print wheel drive motor. The rim plate is formed from a lighter and more readily fabricatable material as compared with the hub.

United States Patent Barrett 1541 DRUM SERIES PRINTER WITH TYPE WHEELSDRIVEN BY INDIVIDUALLY REMOVEABLE MOTORS [72] Inventor: Edgar WhltehouseBarrett, Chateauguay Quebec, Canada [73]. Assignee: Robert MorseCorporation Limited,

Montreal, Quebec, Canada [22] Filed: May 28, 1970 [21] Appl. No.: 41,307

521 user ..101/99,101/95, 101/110 511 mu ..B4lj l/46,B41j 7/36 58FieldofSearch ..101/110,14,75,77,79,s3,

Thut et a1. ..lOl/llOX Primary Examiner-William B. Penn AssistantExaminer-E. M. Coven Attorney-Strauch, Nolan, Neale, Nies & Kurz [5 7]ABSTRACT The printing machine of this invention comprises a Aug. 15,1972 plurality of motor driven printing wheels which are selectivelypositioned to print out a desired line of information on a recordmedium. Each printing wheel is of multi-part construction having ashaft, receiving hub, a rim plate fixed on the hub, and a plurality oftype sectors removably, pivotally mounted on the rim plate. A platendisposed horizontally below the printing wheels is vertically displacedto print the characters on those sectors that are facing verticallydownwardly at'the platen printing position. Each of the sectors is freeto swing under the influence of its own weight about a pivot axisextending parallel to the print wheel rotational axis as the print wheelis rotated so that when the sector is moved] to its downwardly facingprinting position, the weight of the sector,

under the influence of gravity, will swing the sector to a positionwhere the type on the sector is parallel to the printing surface of theplaten. The sectors on each printing wheel are readily removable so thatthey may be replaced or arranged in a difi'erent order on the printingwheel. The print wheel hub is formed separately of the print wheel rimplate and is preferably fabricated from a relatively hard metal tominimize wear due to print wheel rotation. The hub is formed on itsouter periphery with an annular, radially extending land which serves asa spacer for axially spacing the rim plate from a sprocket wheel whichis drive connected by a chain to the print wheel drive motor. The rimplate isformed from a lighter and more readily fabricatable material ascompared with the hub.

8 Claims, 14 Drawing Figures PATENTEDAUB 15 m2 SHEET 1 [1F 9 FIG. I

INVENTOR EDGAR WHITEHOUSE BARRETT PATENTEDAH 15 1 3.683.801

smzn a or 9 INVENTOR.

EDGAR WHITEHOUSE BARRETT ATTORNEYS PATENTEnAus 1 5 I912 3.683.801

SHEET 3 BF 9 INVENTOR EDGAR WHITEHOUSE BARRETT ATTOR N EYS PATENTEDAUB15 1912 SHEET 5 0F 9 INVENTOI EDGAR WHITEHOUSE BARRETT I ATTOR SPATENTEBAHB 1 I912 a 683', 801

SHEET 7 UF 9 [NV ENTOR EDGAR WH ITEHOUSE BARRETT ATTORNEYS PATENTEDAus15 m2 SHEET 8 [1F 9 [NV ENTOR EDGAR WHITEHOUSE BARRETT BY Y 44M ly msPATENTEDAUB 15 m2 SHEET 9 BF 9 H a l all l NN IIIHIIIIII INVENTOR EDGARWHITEHOUSE BARRETT ATTOR N E S DRUM SERIES PRINTER WITH TYPE WHEELSDRIVEN BY INDIVIDUALLY REMOVEABLE MOTORS FIELD OF INVENTION Thisinvention relates to printing machines for printing information on arecord medium.

BACKGROUND, SUMMARY AND OBJECTS OF INVENTION Line printersconventionally comprise a plurality of rotatable printing wheels and avertically displaceable printing platen disposed below the printingwheels. The printing type is conventionally rigidly fixed to theperiphery of each printing wheel. An inked ribbon usually extendsbetween the platen and the printing wheels, and a record medium is fedbetween the ribbon and the platen so that when the platen is raised, thedownwardly facing type on the wheels will print characters on the recordmedium.

Sometimes the printing wheel is not rotated to a precise position wherethe downwardly facing piece of type on the printing wheel periphery isexactly parallel with the platen printing surface. As a result, theprintout of the character will not be uniform, and parts of thecharacter may not be printed at all. This condition particularly occursin printers having stepping motors drive connected to the printing wheelfor stepping the printing wheels to desired printing positions. If theangular displacement made in each step of the motor is not precise, theprinting face of the type representing the desired character may not bein a position where it is parallel with the platen printing surface.

To avoid the foregoing, objectionable condition, this invention providesfor a plurality of separately. formed type sectors which are mounted onthe periphery of the printing wheel or type carrier independently ofeach other for limited, free pivotable displacement about an axisextending parallel to the print wheel rotation axis. Thus, when theprinting wheel is rotated to locate a selected sector in its downwardlyfacing printing position, the sector will swing under its own weightabout its pivot axis to a position where the printing face of the typeon the sector is parallel with the platen printing surface.

According to a further feature of this invention, the sectors arereadily removably mounted on the printing wheel so that they may easilybe replaced. Also, the order in which the sectors are arranged on theprinting wheel can quickly and easily be changed. The sectors of thisinvention have a generally U-shaped configuration to loosely straddlethe periphery of the wheel. A pin carried on the wheel extends throughthe legs of the sector, and the pin is removable to free the sector fromthe wheel.

According to another feature of this invention the printing wheel has ashaft receiving hub which is formed separately from an annular rim platethat peripherally mounts the type sectors. The hub is formed from arelatively hard metal to minimize wear due to print wheel rotation on asupport shaft. The rim plate is fabricated from a softer material sothat it can be formed more easily and at a reduced manufacturing cost.Furthermore, the rim plate is advantageously formed from a material thatis lighter than the hub material to reduce the overall weight of theprinting wheel.

The hub is formed on its outer periphery with radially extending annularland. The rim plate is mounted on the hub axially on one side of theland, and a motor driven sprocket wheel or gear is mounted on the hubaxially on the opposite side of the land so that the land acts as aspacer separating the sprocket wheel from the rim plate by a desiredclearance.

The printing wheels in this invention are driven by separate motors.Each motor is drive connectedto its associated wheel by a drive train.The motors are mounted on separate support plates, and the supportplates are separately removably mounted on a support structure in theprinter. Each support plate also mounts drive train parts that areassociated with the motor support thereon. With this construction, eachmotor and associated drive train parts may be removed from andreassembled in the printer without requiring the removal of any of theother motors or drive train parts. Assembly and disassembly of themotors and drive trains is therefore simplified.

Other objects of this invention will appear as the description proceedsin connection with the appended claims and the below-described drawings.

DESCRIPTION OF DRAWINGS FIG. 1 is a plan view of the printer accordingto a preferred embodiment of this invention with the outer casing of theprinter being broken away to show interior details;

FIG. 2 is a partially sectioned front elevation of the printer shown inFIG. 1; g

FIG. 3 is a side elevation of the printer shown in FIG.

FIG. 4 is an enlarged, fragmentary view in elevation of the printerplaten and the label feed mechanism shown in FIG. 2;

FIG. 5 is a fragmentary section taken substantially along lines 5-5 ofFIG. 4;

FIG. 6 is an enlarged longitudinal section'illustrating the two leftmost printing wheelsshown in FIG. 2;

FIG. 7 is a plan view of one of the type sectors shown in FIG. 6;

FIG. 8 is an enlarged fragmentary view illustrating a cross section ofone of the type sectors on the printing wheel periphery;

FIG. 9 is a schematic illustrating a suitable circuit for energizing theprint wheel motors shown in FIGS. 1-3;

FIG. 10 is an enlarged fragmentary view in plan of one of the printwheel motor drives shown in FIGS. 1-3;

FIG. 11 is a section taken essentially along lines 11-11 of FIG. 10;while FIG. 12 is a section taken substantially along lines 12-12 of FIG.11;

FIG. 13 is a fragmentary plan view of the label feed mechanism shown inFIG. 4; and,

FIG. 14 is a section taken substantially along lines 14-14 of FIG. 3.

DETAILED DESCRIPTION apart support plates 22 and 24. Wheels Wl-W arethus disposed between plates 22 and 24 and are rotatable about a commonaxis. Plates 22 and 24 support shaft 20 and are respectively supportedon rigid, parallel, spaced apart base plates 28 and 30. Support plates22 and 24 are respectively rigidly, removably fixed to base plates 28and 30 by screws indicated at 32.

Base plates 28 and 30 are rigidly mounted on a suitable rigid structuralbase 34 by stud and nut assemblies indicated at 36. A casing enclosingthe printing mechanism is indicated at 38, and is mounted on base 36 asshown. In this embodiment, the axis of shaft 20 extends horizontally.

As best shown in FIG. 4, a rigid printing platen 40 of suitableconstruction is disposed horizontally below printing wheels Wl-Wl0 sothat only the vertically downwardly facing printing type disposed onwheels Wl-WlO and aligning with a vertical axis will print when platen40 is raised. Platen 40 is mounted on a suitable, corrugated, verticallyexpandable bellows 42, and bellows 42 is mounted on a rigid base plate44. Air pressure for expanding bellows 42 and thereby raising platen 40to a printing position is supplied by a suitable source 46 through atwo-position control valve 48. Valve 48 may be operated manually or by asuitable solenoid 50 and may be of any suitable conventionalconstruction which is normally spring biased to a position to exhaustair from bellows 42 and which is actuated by selectively energizingsolenoid 50 to establish fluid communication between source 46 and theinterior of bellows 42 through a pipe line indicated at 52. Thus, in oneposition, valve 28 will exhaust air from bellows 42, to allow a pair ofcoiled, compression springs 54 and 55 to bias platen 40 downwardly toits illustrated, non-printing position. In its other position, valve 48supplies air under pressure to bellows 42, and the air pressure inbellows 42 expands the bellows along a vertical axis to raise platen 40to its printing position against the bias exerted by springs 54 and 55.

When platen 40 is raised the vertically downwardly facing characters onwheels Wl-Wl0 will be printed simultaneously in a single line of print.The printing machine described herein is therefore a line printer inwhich lines of print are successively printed and in which thecharacters in each line are simultaneously printed.

As shown in FIGS. 4 and 5, springs 54 and 55 respectively peripherallysurround vertical guide rods 56 and 57 which are fixed at their upperends to platen 40. Rods 56 and 57 slidably and coaxially extend throughguide sleeves 56a and 57a. Sleeves 56a and 57a are fixed at their lowerends in apertures in base plate 44. Rods 56 and 57 are threaded at theirlower ends to respectively receive nuts 58 and 59. Spring 54 is axiallycompressed between the underside of base plate 44 and a washer 60 whichis seated on nut 58. Spring 55 is axially compressed between theunderside of base plate 44 and a washer 61 which is seated on nut 59.

As shown, rods 56 and 57 are parallel with each other and with thevertical expansion axis of bellows 42. A vertical plane containing theaxes of rods 56 and 57 together with the vertical expansion axis ofbellows 42 normally intersects the flat upwardly facing printing surfaceof platen 40 and also contains the longitudinal axis of shaft 20 aboutwhich wheels Wl-Wl0 are rotatable. Rods 56 and 57 are spacedequidistantly on opposite sides of bellows 42.

When pressurized air is exhausted from bellows 42, springs 54 and 55,which react against the underside of base 44, resiliently urge platen 40vertically downwardly to a non-printing position where the top printingsurface of platen 40 is out of contact and spaced below the printingtype on wheels W1-Wl0.

Still referring to FIG. 4, each of the rods 56 and 57 is formed withupwardly facing, annular shoulders 64 which act as stop faces and whichseat against the underside of base plate 44 upon expansion of bellows 42to stop upward movement of platen 40 at its platen printing position.Since bellows 42 is made of a yieldable material, it cannot preventtilting of platen 40 under the influence of non-symmetrical printingforces. However, seating engagement of shoulders 64 against theunderside of base plate 44 prevents platen 40 from tilting away from itsuntilted printing position under conditions where non-symmetrical forcesare applied to platen 40 when it strikes the printing type on wheelsWl-W10 through a suitable inked, printing ribbon 66 and a suitable formof record medium 68 on which desired information is to be printed. Thisnon-symmetrical force condition can occur if non-symmetrically disposedprinting wheels are rotated to locate blank (i.e., non-printing)character spaces at the platen printing position. As will be describedin greater detail later on, each of the print wheels Wl-Wl0 usually hasat least one blank character space where no character is printed.

If platen 40 is tilted under the influence of the nonsymmetrical forcecondition mentioned above, some printing type on the print wheels mightnot be struck by the record medium 68 on platen 40, or the strikingforce might not be uniform for all of the printing wheels. Tilting ofplaten 40, however, is avoided by the seating engagement of shoulders 64against the underside of base plate 44.

As best shown in FIG. 6, wheel W10 comprises a series of separatelyformed type sectors 70, a sectormounting annular rim plate 72, and a hub74 which is formed separately of plate 72. Hub 74 is formed with auniformly diametered through bore 76 which coaxially, rotatably receivesshaft 20. The opposite end faces of hub 74 are respectively indicated at78 and 79. End faces 78 and 79 are flat and are contained in parallelplanes normally intersecting the print wheel rotational axis.

Still referring to FIG. 6, the outer periphery of hub 74 is stepped tointegrally provide a raised, radially extending annular portion 80between two reduced diametered axially aligned boss portions 82 and 83.Boss portions 82 and 83 are each formed with smooth uniformly diameteredcylindrical peripheries. Boss portion 82 axially extends between endface 78 and portion 80, and boss portion 83 axially extends betweenportion 80 and end face 79. The intersection of portion 80 with bossportions 82 and 83 respectively formed annular shoulders 84 and 85 whichface axially in opposite directions and which are contained in parallel,radial planes.

Still referring to FIG. 6, plate 72 is coaxially and nonrotatably pressfitted on boss portion 82 and is staked in place where it firmly seatsagainst shoulder 84. On the opposite side of portion 80, a motor driven,chain sprocket wheel 88 is mounted on boss portion 83 and is firmlyseated against shoulder 85. Wheel 88 is non rotatably fixed to hub 74 bya roll pin 89 which coaxially extends through small, axially aligned,axially extending through bores in wheel 88, portion 80 and plate 72.

From the construction of wheel W thus far described, it will beappreciated that plate 72 and sprocket wheel 88 are on axially oppositesides of portion 80 and that portion 80 functions as a spacer forspacing plate 72 and sprocket wheel 88 axially apart by the pre-selectedaxial dimension of the land. For replacement or repair, plate 72 andsprocket wheel 88 can be removed from hub 74 independently of eachother. Thus, the previously described construction of hub 74 and thearrangement of plate 72 and sprocket wheel 88 on hub 74 provides thedesired clearance between plate 72 and wheel 88, simplifies the assemblyand disassembly of the subassembly of plate 72, wheel 88, and hub 74,and particularly enables removal of plate 72 without requiring removalof wheel 88 aswell as enabling removal of wheel 88 without requiringremoval of plate 72.

Preferably, hub 74 is formed from a suitable tool steel or relativelyhard, suitable material to reduce wear caused by rotation of the hub onshaft 20. Since plate 72 and hub 74 are separately formed according tothis invention, plate 72 is advantageously formed from 7 aluminum orother similar metal which can be easily fabricated into the desired partas by stamping. By making plate 72 from a readily fabricatable metalsuch as aluminum, the weight of the complete print wheel assembly issignificantly reduced as well as reducing costs of manufacture. Thus themulti-component print wheel assembly provides the combined advantage ofminimized wear due to print wheel rotation, relatively low manufacturingcosts, ease of assembly and disassembly, and lightness in weight.

As shown in FIGS. 5, 6, 7 and 8, each of the type sectors comprises atype-mounting sector element 90 and a type element 92 in the form of thedesired character to be printed. Sector element 90 is formed with a pairof parallel, spaced apart arm portions 94 and 95 which are integrallyjoined together by a cross piece 96. Cross piece 96 is in the form of abasefor mounting type element 92. The outwardly facing surface of crosspiece 96 is advantageously flat as shown. Type element 92 is seated onthe outwardly facing flat cross piece surface and is rigidly fixed tocross piece 86 by any suitable means.

Each sector element 90 is seated over the outer peripheral portion ofplate 72 and straddles the outer peripheral portion of plate 72, witharm portions 94 and 95 being disposed on opposite sides of the plate asbest shown in FIGS. 6 and 8. Each sector element 90 is removably securedto plate 72 by a small, cylindrically smooth pin 98 that slidably andcoaxially extends through small, aligned apertures in arm portion 94,plate 72, and arm portion 95. Removable lock rings 100 mounted onopposite ends of pin 98 secure the subassembly of pin 98 and sectorelement 90 on the rim portion of plate 72. Each of the sectors 70 areremovable independently of each other first by removing lock rings 100and then by removing pin 98. Sector 70 is then free for removal simplyby sliding it radially off the rim portion of plate Arm portions 94 and95 are loosely mounted on pin 98,- and there furthermore, is sufficientclearance between each of the arm portions and plate 72 and also betweencross section 96 and the periphery of plate 72 so that each sector 70 isfreely pivotable or swingable about the longitudinal axis of pin 98under the influence of its own weight. The longitudinal axis of pin 98is parallel with the rotation axis of the printing wheel. Thus when eachsector 70 is advanced to the platen printing position (as indicated atl0lin FIG. 5) by rotation of the printing wheel for printing a desiredcharacter, the sector will swing under the influence of its own weightto a position where the printing face of the type element 92 is parallelwith the printing surface of platen 40. Uniform printing ofadesiredcharacter is therefore ensured, even though the sector is not preciselyat the platen printing position where a plane extending perpendicularlyof the platen printing surface and containing the rotational axis of theprinting wheel also contains the axis of pin 98 and medially intersectsthe sector 70. If the axis of pin 98 is slightly angularly displacedfrom this plane: as viewed from FIG. 5, the weight of the sector exertsan eccentric force on the sector to pivot it to a position where theprinting face of type element 92 is parallel with the flat printingsurface of platen 40. Consequently, slight inaccuracies in setting upthe printing wheel for printing desired characters do not result in anon-uniform printout of the desired character. It will be noted thatcentroid of sector 70 is closer to cross piece 96 thanto pin 98 so thatthe sector always tends to swing to a position where type element 92 islevel and facing downwardly.

Furthermore, the foregoing construction of sector 70 and the manner ofmounting it on plate 72 enables each sector to be readily removed forreplacement or repair. Thus, where it is desired to print one or moredifferent characters, the sectors can readily be replaced with sectorshaving type for printing the desired characters. Also, the order inwhich the characters are positioned on the printing wheel can be changedquickly and easily to provide a desired order of printing type on thewheel. This feature is particularly advantageous when the printer isused with a control system that sets up the printing wheel for printinga desired character by rotating the wheel in one direction or the otherfrom a predetermined home position to the desired printing position andthen returns the wheel to the aforesaid home position after thecharacter is printed by rotating the wheel in the opposite direction. Insuch an arrangement, the previously mentioned home position is theposition of the printing wheel where a blank character space such asthat indicated at 102 in FIG. 5 is located at the platen printingposition. When the printing wheel is in this position, no character willbe printed. An example of the control circuitry for rotating theprinting wheels in the manner just described is disclosed in thecommonly assigned copending application Ser. No. 41429 filed on May 28,1970 for ALPHA NUMERIC RECORDING SYSTEM. With such a system the totalangular displacement of the printing wheel for rotating it from the homeposition to the printing position and then rotating it back to the homeposition from the printing position in preparation for printing the nextdesired character may be minimized by judicially locating the sectorshaving the most frequently printed characters closest to the homeposition 102. If the information to be printed is changed for somereason, the sectors, being readily and easily removable, can then berearranged in a new order where the sectors having the most frequentlyprinted characters are again positioned closest to the home position.

Except for one or more blank character spaces as indicated at 102 inFIG. 5, sectors 70 are spaced equiangularly apart by a distancesufficient to allow each sector to pivot about its pin 98 so that itwill be properly positioned for printing its type element 92 withoutinterference from adjacently disposed sectors.

The construction of each of the printing wheels W1-W9 is the same asthat just described for printing wheel W10. Accordingly, like referencenumerals have been applied to designate like parts.

As shown in FIGS. 2 and 6, annular spacers 103 and 105 are mounted onshaft 20 for confining the assembly of printing wheels Wl-W againstaxial displacement. Spacer 103 is axially confined between plate 24 andthe hub of wheel W10, and spacer 105 is axially confined between plate22 and the hub of wheel W1.

As best shown in FIGS. 1-3, a series of motors MWl, MW2, MW3, M W4, MW5,MW6, MW7, MW8, MW9 and MW10 are respectively connected to wheels W1-W10by drive trains indicated at 110 for rotating each of the printingwheels. Motors MWl-MW10 may be of the reversible, stepping type and maybe of any conventional form such as the Superior Electric Slo Syn ModelS8250 which has four input terminals to which pulses are applied forstepping the motor in one direction or the other as generally indicatedon page 271 of the 1968 Edition of the Digital Logic Handbook publishedby the Digital Equipment Corporation of Maynard, Massachusetts. As shownin FIG. 9, each of the motors MWl-MW10 is energized by a suitable driver1 12 which may be of any conventional type such as that described onpage 271 of the previously identified Digital Logic Handbook. Properlysequenced pulses are supplied to each driver 112 by a suitabletranslator ll4'which may be of the type shown in FIG. 2 on page 272 ofthe previously described Digital Logic Handbook. Pulses for activatingthe translators 114 may be derived from any suitable form of pulsegenerator 116 which produces a train of pulses at a preselectedfrequency. It will be appreciated that any suitable form of circuitrymay be utilized for energizing and controlling operation of motorsMWl-MWIO. It also will be appreciated that operation of motors MWl-MW10may be controlled by the circuitry disclosed in the previouslyidentified copending application Ser. No. 41429. Switches 117 FIG. 9) orany other suitable means may be utilized for controlling the applicationof pulse generator pulses to translators 114.

Still referring to FIGS. 1-3, motors MW1-MW7 are arranged in a stepped,spiral path around the longitudinal axis of shaft 20. Motors MW8-MW10are arranged in a second stepped, spiral path, behind motors MW1-MW3.The rotational armature shaft axes of motors MWl-MWIO are parallel witheach other and with the aligned rotational axes of wheels W1-W10.

As shown in FIGS. 1-3 and 14, a series of parallel, spaced apart,threaded tie rods 128a, 128b, 1280, 128d,

128e, l28f, 128g, and 128k are provided for supporting motors MWl-MW10between plates 22 and 24. One end of each of the rods l28ah is fixed toplate 22 by nuts indicated at 133. The opposite end of each of the rods128a-h is fixed to plate 124 by nuts indicated at 135.

Motors MW 1-MW10, as shown in FIGS. l-3, are respectively mounted onseparately formed plates a, 120b, 1200, 120d, 120e, 120f, 1203, 120k,120i, and l20j. The downwardly facing edge of each of the plates 120a-jis formed with a pair of outwardly opening, spaced apart notches 131 and137 (see FIG. 11).

As best shown in FIG. 14, rods 128a and 128!) respectively extendthrough the notches 131 and 137 in plate 120a, and these rods alsoextend through the notches 131 and 137 in plate 120h. Rod 128b alsoextends through the notches 131 in plates 120b and 120i. Rod l28cextends through notches 137 of plates 12% and 120i and also throughnotches 131 of plates 120c and l20j. Rod 128 d extends through notches137 of plates 120s and l20j and also through notch 13] of plate 120d.Rod l28e extends through notch. 137 of plate 120d and also through notch131 of plate l20e. Rod 128f extends through notch 137 of plate 120e andalso through notch 131 of plate 120f. Rod 128g extends through notch 137of plate 120]" and also through notch 131 of plate 120g. Rod 128hextends through notch 137 of plate 120g.

Two pairs of nuts 134a and 136aare provided for releasably fixing plate120a on rods 128a and 128k. The nuts of pair 134a are threaded on rod128a on opposite sides of notch 131, and the nuts of pair 136a arethreaded on rod l28b on opposite sides of notch 137 to securely clampplate 120a against movement on rods 128a and 128b. Plate 120b issimilarly releasably clamped in place on rods l28b and 1286 by two pairsof nuts 134b and 136b. The nuts of pair 134b are threaded on rod 128b onopposite sides of plate 120b, and the nuts of pair l36b are threaded onrod 1280 on opposite sides of plate 120b.

Plate 1200 is also releasably clamped by two pairs of nuts 134c and 1360on rods 128c and 128d. The nuts of pair 1346 are threaded on rod 1286 onopposite sides of plate 1200, and the nuts of pair 136c are threaded onrod 128d on opposite sides of plate 120c.

Plate 120d is similarly releasably clamped by two pairs of nuts 134d and136d on rods 128d and 128a. The nutsof pair 134d are threaded on rod128d on op posite sides of plate 120d, and the nuts of pair 136d arethreaded on rod 128e on opposite sides of plate 120d.

Plate 128e is also releasably clamped by two pairs of nuts 134e and l36eon rods 128e and l28f. The nuts of pair 134e are threaded on rod 128e onopposite sides of plate 120e, and the nuts of pair 136e are threaded onrod 128f on opposite sides of plate l20e.

Similarly, plate 120f is releasably clamped against movement on rodsl28f and 128g by two pairs of nuts 134f and 136f. The nuts of pair 134fare threaded on rod 128f on opposite sides of plate 120f, and the nutsof pair 136f are threaded on rods 128g on opposite sides of plate 120f.

Likewise, plate 120g is releasably clamped against movement on rods 1283and 128k by two pairs of nuts 134g and 136g. The nuts of pair 134g arethreaded on rod 128g on opposite sides of plate 120g, and the nuts ofpair 136g are threaded on rod 128 on opposite sides of plate 120g.

Plate 120k is also releasably clamped against movement on rods 128a and1281) by two pairs of nuts l34h and 136h. The nuts of pair 134/1 arethreaded on rod 128a on opposite sides of plate 120k, and the nuts ofpair 136k are threaded on rod l28b on opposite sides of plate 120k.

Similarly, plate 120i is releasably clamped against movement on rods128b and 1280 by two pairs of nuts 134i and 136i. The nuts of pair 134iare threaded on rod 128k on opposite sides of plate 120i, and the nutsof pair 136i are threaded on rod 128c on opposite sides of plate 120:.

Finally, plate 120j is releasably fixed on rods 1280 and 128d by twopairs of nuts 134] and 136j. The nuts of pair 134j are threaded on rod128c on opposite sides of plate 120j, and the nuts of pair 136j arethreaded on rod 128d on opposite sides of plate 120j.

Each of the plates 120a-j extend in parallel planes which normallyintersect the axes of the tie rods upon which they are mounted. Each ofthe motors MWl-MW10 has an armature shaft 122 extending freelythrough anaperture in its associated support plate (120a-j).

From the foregoing it is clear that each motor MW1MW10 is mounted on aseparate support plate (120a-j and that each of the support plates(120a-j) is detachably mounted on two of the rods 128a-h. Rods b-g areeach used as a common support for adjacent motor support plates. Inaddition to mounting the motor support plates, rods 128a-h rigidlysecure plates 22 and 24 together.

As best shown in FIGS. 10 and 11, the drive train 110 for impartingrotation to wheel W1 comprises a pair of sprocket wheels 140 and 142 andan endless drive chain 144. Sprocket wheel 140 is fixed on the free endof armature shaft 122, and sprocket wheel 142 is mounted for rotation onplate 120a in a suitable manner. Chain 144 is trained over sprocketwheels 140, 142, and 88 to thus transmit rotation of armature shaft 122for rotating wheel W1 in one direction or the other.

The drive trains 110 for operatively connecting motors MW2-MW10respectively to wheels W2-W10 is the same as that just described formotor MWI and wheel W1. Accordingly, like reference numerals have beenapplied to designate like parts for the motor support structures formotors MW2-MW10 and for the drive train for connecting motors MW2-MW10respectively to wheels W2-W10.

From the foregoing description, it will be appreciated that motorsMW1-MW10 are mounted independently of each other on their respectivesupport plates 120. Furthermore, the sub-assembly of each print wheeldrive motor, its associated support plate (la', sprockets 140 and 142,and chain 144 is independently mounted on plates 22 and 24 so that itcan be removed and reassembled without requiring the removal andreassembly of any of the other sub-assemblies. With this constructionand arrangement, the assembly and disassembly of motors MWl-MWIOtogether with associated drive train parts is simplified to minimize thetime and costs involved in repairing or replacing the component parts.

For example, to remove motor MW] and its associated support plate a, itis only necessary to loosen either nuts 134a and 136a to free plate120a. The sub-assembly of plate 120a and motor MWI may then be liftedout of the printer after chain 144 is untrained from sprocket wheel 88.Also, by loosening the nuts 134a and 1360, plate 120a may berepositioned by swinging it in one direction or the other about thelongitudinal axes of rods 128a and 128b to adjust the tension in chain144.

The stepped, spiraled arrangement of motors MWl-MWIO provides for acompact arrangement to minimize the space required for the printingmechanism. This arrangement also enables more than one motor supportplate to be mounted on each of the rods 128a-h.

I By removably mounting plates 22 and 24 respectively on plates 28 and30, the entire sub-assembly of plates 22 and 24 including the partssupported thereon including motors MW1-MW10 and wheels Wl-W10 may beremoved as a complete unit from the printer. This sub-assembly of plates22 and 24 and the component parts that are mounted thereon is simply andeasily removed by removing screws 32. As shown in FIG. 2, the upperedges of plates 28 and 30 are notched so that each plate is formed witha recessed ledge 137 and a guide portion 138. Plates 22 and 24 areseated on ledges 137 of base plates 28 and 30 between portions 138 sothat the sub-assembly of plates 22 and 24 and the parts mounted thereonremain supported on plates 28 and 30 after screws 32 are removed.

The record medium 68 may be of any suitable form such as a label, ticketor sheet. Labels may be joined 7 together by transverse perforations inthe form of an elongated sheet on which desired information is printedout.

As shown in FIGS. 4 and 13, a suitable label-feeding mechanism comprisesa pair of parallel spaced apart catapiller track assemblies 140 and 141which are of conventional construction and which are disposed onopposite sides of a label-feed passage 144 (see FIG. 3) which are formedin the printer by guide members indicated at 146.

Assembly 141, as best shown in FIG. 5, comprises an endless catapillertrack trained around paralle spaced apart pulleys 152 and 153 which arerespectively fixed on a pair of parallel spaced apart shafts 154 and155.

Assembly 140 is the same as assembly 141, like reference charactersbeing applied to designate like parts. The pulleys 152 and 153 ofassembly 140 are respectively fixed on shafts 154 and 155. Each of theshafts 154 and 155 is journalled at its opposite ends on plates 28 and30 by any suitable means. Shaft 155, as best shown in FIG. 13, is driveconnected to a label feed motor by a suitable gear train indicated at162. Motor 160 may selectively be energized by any suitable means forrotating shaft 155 to advance catapiller tracks 150. Tracks 150 areprovided with pins 164 (see FIG. 4) which extend through perforations inthe marginal side edges of the label or other sheet of paper insertedinto passage 144. Thus, energization of motor 160 feeds the label orother sheet through passage 144 and between platen 40 and the array ofprint wheels W1-W10.

As best shown in FIGS. 1 and 2, a ribbon feed mechanism 170 may be ofany suitable construction for advancing and rewinding ribbon 66. Onesuitable arrangement comprises a pair of motors M1 and M2 and a pair ofribbon spools 172 and 173. Motors M1 and M2 respectively aredrive-connected to spools 172 and 173 by suitable clutches C1 and C2.The opposite end portions of ribbon 66 are wound around spools 172 and173 in the usual manner.

Ribbon 66 extends from spool 172 and passes under an idler pulley 174.From pulley 174, ribbon 66 passes horizontally between platen 40 and thearray of printing wheels Wl-WlO at right angles to the path along whichthe labels or other sheets are advanced through the printer. The centerline of ribbon 66 is contained in a vertical plane extending radiallyfrom the rotational axis of wheels Wl-W and normally intersecting theflat printing surface of platen 40. On the opposite side of platen 40,ribbon 66 is trained around another idler pulley 176 and then may passhorizontally back between platen 40 and the array of printing wheelsWl-W10 to a region where it trains over a further idler pulley 178 andpasses to spool 173. The label feed mechanism advances the labels orother sheets between platen 40 and the tensioned portions of ribbon 66that extend between wheels Wl-W10 and the platen 40. Thus when platen 40is raised, the printing type facing vertically downwardly will beprinted on the label. Energization of motors M1 and M2 and clutches C1and C2 may be selectively controlled in any suitable, conventionalmanner to advance ribbon 66 and to reverse or rewind the ribbon.Energization of motors M1 and M2 together with clutches Cl and C2 mayalternatively be correlated with the operation of the label feedmechanism in a manner disclosed in the previously identified copendingapplication Ser. No. 41429 Each of the ribbon spools 172 and 173 isfree-wheeling in a direction opposite to the direction in which it isrotated when its associated motor and clutch are energized.

To operate the printer, the record medium 68 is inserted into passage144, and motor 160 is energized to advance the record medium betweenribbon 66 and platen 40 to a position where the first line of print isto be printed. Each of the print wheels W1-W10 is set up for printing adesired character by closing its associated switch 117. By closing eachswitch 117 the associated print wheel drive motor is energized to rotatethe associated print wheel. When the desired character on each printwheel is advanced to the platen printing position, the associated switch117 is opened to stop rotation of the wheel. The valve 48 is actuated tointroduce pressurized air into bellows 32. As a result, platen 40 willbe raised to print the line of selected characters on record medium 68.If it is desired to print a second line on the record medium, motor 160is reenergized to advance the record medium to the position where it isdesired to print the second line. Wheels Wl-WIO are then re-positionedto print the desired information in the second line, and platen 40 isthereafter raised to print the second set of selected characters in thesecond line.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not restrictive, the scope of the invention being indicated by theappended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent is:

1. In a printing apparatus, opposed, spaced apart, rigid shaft-supportmembers, a support shaft extending between said members and beingsupported at opposite ends by said members, and a plurality of motor andtype carrier assemblies each comprising a type carrier rotatably mountedon said shaft, type positioned on the periphery of said carrier forprinting characters, a type carrier drive motor having a rotatable poweroutput shaft, motion transmitting means drive connecting said outputshaft to said carrier for imparting rotation of said power output shaftto said carrier, and means for removably mounting said motor betweensaid shaftsupport members the motors of said assemblies being removablysupported independently of each other by their respective mountingmeans, and the mounting means of said assemblies providing for theremoval of the motor in each of said assemblies without requiring theremoval of the motors in any of the other of said assemblies.

2. The printing apparatus defined in claim 1 wherein said mounting meansof each of said assemblies comprises plate means, with each motor havinga housing fixed to said plate means, said plate means being formed withan outwardly opening notch along an edge thereof, and each of saidassemblies further comprising at least one elongated, threaded memberextending through said notch and being fixed at opposites to saidshaft-support members, and means threaded on said threaded member andreleasibly clamping said plate means on said threaded member, said meansthreaded on said threaded member being selectively releasible to providefor the removalof said plate means and said motor as a unit.

3. The printing apparatus defined in claim 2 wherein said means threadedon said threaded members comprises a pair of parts seated againstopposite sides of said plate means in the region of said notch to clampsaid plate means therebetween.

4. The printing apparatus defined in claim 3 wherein said motiontransmitting means of each of said assemblies comprises first and secondpower transmitting members respectively coaxially fixed to said carrierand the power output shaft of said motor and a tensionable, endless,flexible member trained over said power transmitting members for driveconnecting said second member to said first member, the rotational axesof said carrier and said power output shaft being parallel with eachother and with the longitudinal axis of said threaded member, and saidplate means being selectively swingable about the longitudinal axis ofsaid threaded member to adjust the tension in said endless member wheneither or both of said parts are threaded to positions where they arereleased from clamping engagement with said plate means.

5. The printing apparatus defined in claim 4 compris ing support basemeans, means releasably mounting said shaft-support members on said basemeans to provide for the removal of said support members, said l3 l4shaft, and said assemblies as a unit from said base 7. The printingapparatus defined in claim 1 wherein means. the rotational axis of eachpower output shaft of said 6. The printing apparatus defined in claim 1wherein assemblies is parallel with the longitudinal axis of saidrotational axes of the motors of said assemblies are PPOH Shaft vparallel with each other and with the longitudinal axis 5 The Printingapparatus defined in claim 1 wherein of said support shaft, and whereinsaid motors are an sald arraflged and supfponed F a Cuff/5d ranged dsupported i a Stepped spiral path extend, path extending partiallyaround the longitudinal axis of ing partially around the longitudinalaxis of said sup- Said Support shaft port shaft. 10 I

1. In a printing apparatus, opposed, spaced apart, rigid shaftsupport members, a support shaft extending between said members and being supported at opposite ends by said members, and a plurality of motor and type carrier assemblies each comprising a type carrier rotatably mounted on said shaft, type positioned on the periphery of said carrier for printing characters, a type carrier drive motor having a rotatable power output shaft, motion transmitting means drive connecting said output shaft to said carrier for imparting rotation of said power output shaft to said carrier, and means for removably mounting said motor between said shaft-support members the motors of said assemblies being removably supported independently of each other by their respective mounting means, and the mounting means of said assemblies providing for the removal of the motor in each of said assemblies without requiring the removal of the motors in any of the other of said assemblies.
 2. The printing apparatus defined in claim 1 wherein said mounting means of each of said assemblies comprises plate means, with each motor having a housing fixed to said plate means, said plate means being formed with an outwardly opening notch along an edge thereof, and each of said assemblies further comprising at least one elongated, threaded member extending through said notch and being fixed at opposites to said shaft-support members, and means threaded on said threaded member and releasibly clamping said plate means on said threaded member, said means threaded on said threaded member being selectively releasible to provide for the removal of said plate means and said motor as a unit.
 3. The printing apparatus defined in claim 2 wherein said means threaded on said threaded members comprises a pair of parts seated against opposite sides of said plate means in the region of said notch to clamp said plate means therebetween.
 4. The printing apparatus defined in claim 3 wherein said motion transmitting means of each of said assemblies comprises first and second power transmitting members respectively coaxially fixed to said carrier and the power output shaft of said motor and a tensionable, endless, flexible member trained over said power transmitting members for drive connecting said second member to said first member, the rotational axes of said carrier and said power output shaft being parallel with each other and with the longitudinal axis of said threaded member, and said plate means being selectively swingable about the longitudinal axis of said threaded member to adjust the tension in said endless member when either or both of said parts are threaded to positions where they are released from clamping engagement with said plate means.
 5. The printing apparatus defined in claim 4 comprising support base means, means releasably mounting said shaft-support members on said base means to provide for the removal of said support members, said shaft, and said assemblies as a unit from said base means.
 6. The printing apparatus defined in claim 1 wherein rotational axes of the motors of said assemblies are parallel with each other and with the longitudinal axis of said support shaft, and wherein said motors are arranged and supported in a stepped spiral path extending partially around the longitudinal axis of said support shaft.
 7. The printing apparatus defined in claim 1 wherein the rotational axis of each power output shaft of said assemblies is parallel with the longitudinal axis of said support shaft.
 8. The printing apparatus defined in claim 1 wherein said motors are arranged and supported along a curved path extending partially around the longitudinal axis of said support shaft. 